The ISI used the prepaid telephone SIM card from near the Attari-Wagah border to be in touch with its moles in Jammu and Kashmir, where three men have been arrested for getting calls and WhatsApp messages from that number.
The SIM card was issued in the name of a woman, Rohini Gomes, in Laxmi Nagar in east Delhi, a highly-placed source told IANS. "No such woman ever lived or lives at the Laxmi Nagar address."
The Crime Branch of Delhi Police made the discovery after busting a pan-India ISI-backed espionage racket towards the end of November 2015.
An officer of the Crime Branch, which busted the ISI espionage racket by arresting Kafaitullah Khan from the New Delhi Railway Station on November 26, said the SIM card belonged to a leading cellular service provider.
"An ISI operative used the Delhi number from the India-Pakistan border to contact his agents in India. The number was issued from Delhi on a fake identity card," Joint Commissioner of Police (Crime Branch) Ravindra Yadav told IANS.
Another officer told IANS: "It was a prepaid number and was being used to send messages through WhatsApp."
"The SIM number was actively used near the Attari border through Indian towers without paying international roaming charges," he added.
Delhi Police arrested six suspected ISI moles in November-December 2015.
The six included a serving leading aircraftsman Ranjith K.K., library assistant Kafaitullah Khan, Border Security Force head constable Abdul Rasheed, retired army havildar Munawwar Ahmad Mir, rifleman Farid Khan of the Jammu and Kashmir Light Infantry, and a government teacher, Sabar.
The officer said Kafaitullah Khan, Mir and Sabar were in touch with their ISI handler, identified as Faizal, who was using the number.
"We are also trailing the man who provided the activated SIM card to Faizal, whose real identity is yet to be ascertained."
On December 30, police arrested Ankush Khandelwal from Delhi for issuing several SIM cards on the strength of fake identity cards. A total of 205 pre-activated SIM cards were recovered from Khandelwal.
A 33-year-old man from Shakurpur in west Delhi, Mohit Gupta, was arrested on January 4 for his involvement in creating fake identity cards for those without any residence proof.
"Several fake identity cards and blank customer acquisition forms (CAFs) were recovered from Mohit. On his personal laptop, we found more than 1,000 such fake cards and equal number of photographs of different persons in a folder," the officer said.
Mohit reportedly used these fake identity cards for getting SIM cards activated and to sell these for Rs.500-700 each -- without obtaining any identification documents from the purchaser.
"Mohit also created identity cards for those who had no address proof in Delhi," the officer added.